1. Field of the Invention
The present invention relates to a measuring device for registering a test signal from a circuit structure applied to a wafer (circuit carrier, for example, made from a semiconductor material).
2. Discussion of the Background
During the course of manufacturing integrated circuits, such as amplifier circuits, of which a plurality are disposed on a wafer, it is important to be able to determine as quickly as possible which of these integrated circuits are functional. Progressively smaller circuit structures have led to increased failure rates during the production process. If the functioning of the integrated circuits were only to be checked after they had been integrated in their housing, this would lead to unnecessary costs for the required production steps. To achieve savings in production costs, the functioning of the integrated circuits is checked even before they are separated from the wafer. For this purpose, each integrated circuit contains small test terminals, so-called pads, to which test signals can be applied and measured. These test terminals are subsequently used for the attachment of bonding wires. Special wafer-measuring devices (English: wafer-probers) which provide very small test probes and can be adjusted very accurately in their spatial positioning are required for these measurements.
A device for checking the functioning of individual circuit structures applied to a wafer is known from WO 00/79293 A1. In this context, the wafer to be checked is clamped to a height-adjustable support and pressed against needles mounted in an elastic manner. The needles themselves are connected to a test printed-circuit board. In this context, the test printed-circuit board is connected to the sensor head via an elastic connection. The test printed-circuit board is supplied with current and test signals via the sensor head and reroutes the received test signals to the latter.
The disadvantage with WO 00/79293 A1 is that the device is only suitable for measuring low-frequency signals. However, if the signal power of integrated high-frequency amplifier circuits is to be measured, the device described is associated with various disadvantages. Because the high-frequency test signal is only evaluated within the sensor head, reflections which falsify the test signal arise at various intermediate positions. This is attributable to the long line distance which, under some circumstances in the case of a high-frequency test signal, can be several wavelengths long. Such positions are, for example, the transition from the needle to the test printed-circuit board or from the test printed-circuit board via the elastic connection to the sensor head in which the signal evaluation is disposed, so that a high-frequency test signal can no longer be securely registered with this device.